The IMEI you entered does not appear to be an AT&T wireless phone or tablet...etc

I am trying to unlock my iPhone @ https://www.att.com/deviceunlock/request/#/unlockstep1

Every time I try, I get the same message --> "The IMEI you entered does not appear to be an AT&T wireless phone or tablet. Please re-enter the correct 15-digit IMEI number for your AT&T wireless phone or tablet. You can obtain the IMEI number from the wireless phone by dialing *#06#."

I cleared the cache in my browser and used different browsers with the same result!

I sent a private message to ATTCares (Aug 4, 2017 10:38 PM) that have my name, IMEI and email address...

What should I do next?

Thanks,

Rasha